Road treadle switch



NOV. 7, 1967 W C. GOBLE ROAD TREADLE SWITCH A:2 sheets-shewL 1 FiledJuly a, 1966 E/ E PM M HM 2/ 05/ ,Z s/V/A 4.1.. Z/ l W f ATTORNEY w. c.GOBLE 3,351,724

ROAD TREADLE SWITCH Nov. 7, 1967 Filed July 8, 1966 2 Sheets-Sheec 2INVENTOR W/c/HM 6'. 60am.:

United States Patent() 3,351,724 ROAD TREADLE SWITCH William C. Goble.East Paterson, NJ., assignor to Raybestos-Manhattan, Inc., Passaic, NJ.,a corporation of New Jersey Filed .lilly 8, 1966, Ser. No. 563,756 8Claims. (Cl. 200-86) This invention relates to -a road treadle switch.

The prime object of the present-invention isdirected to a road treadleswitch of the type in which an envelope of elastomeric material encasesswitch members operated by treadle depression of a passing vehicleIapplied to and acting on the top wall of the envelope, the treadleswitch embodying means for improving the wear resistance and thus thelife expectancy thereof while still providing and retaining theflexibility necessary for proper treadle switch operation.

Road treadle switches have been manufactured with envelopes or shellsm-ade of an elastomeric material so as to provide flexibility requiredfor transmitting pressure applied thereto tothe encased switch contacts.The envelopes are usually constructed to embody some modifying or addedmeans for enhancing to a predetermined desired degree the flexibility ofthe top wall thereof in the areas that are subject to treadledepression. The elastomeric top wall of the treadle switch, subjected torepeated depressing and scufing action of the wheels of a vehiclestopping at and starting from a toll station normally wear relativelyfast, and in the'course of time render the treadle inoperative,requiring frequent replacements. The means employed to enhance theflexibility of the treadle top is such that it undesirably acts toincrease the wear and thus more rapidly reduce the useful life of thetreadle, particularly in those parts thereof which are in the path ofthe Vehicle wheels.

In carrying out the prime object of the present invention, the roadtreadle m-ade of an elastomeric material possessing an inherentresilience and abrasive resistance, and an inherent as Well as an addedenhanced flexibility is combined with wear improving means incorporatedinto surface areas of the top wall of the elastomeric envelope betweenand spaced by .adjoining flexibility areas thereof, said meanscomprising wear pads having abrasive resistance greater than theinherent resistance of said adjoining flexibility areas, with the resultthat the wear resistancev of the switch treadle and hence the lifeexpectancy thereof is improved while the necessary and predeterminedflexibility is provided and retained.

To the accomplishment of the foregoing objects and such other objects asmay hereinafter appear, my invention relates to the road treadle switchas defined in the n appended claims taken together with the followingspecification thereof and the accompanying drawings, in

which:

FIG. l is a top plan view of a first form of a road treadle switchembodying the principles of the present invention;

FIG. 2 is a view thereof shown on lan enlarged scale and taken incross-section inthe plane of the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary view thereof shown on the same scale as FIG. 2and taken in cross-section in the plane of the line 3--3 of FIG. 1; Y

3,351,724 Patented Nov. 7, 1967 FIG. 4 is a top plan view of a secondform of a road treadle switch of the invention;

FIG. 5 is a view ofthe latter shown on an enlarged scale and taken incross-section in the plane of the line S-S of FIG. 4;

FIG. 6 is a fragmentary view thereof shown on the same scale as FIG. 5and taken in cross-section in the plane of the line 6-6 of FIG. 4; v

FIG. 7 is a plan view of a modification of the second form of theroadvtreadle switch of the invention;

FIG. 8 is a view of the latter shown on an enlarged scale and taken incross-section in the plane of the line 8-8 of FIG. 7; and

FIG. 9 is a fragmentary view thereof shown on the same scale as FIG. 8and taken in cross-section in the plane of the line 9-9 of FIG. 7.

Referring now more in detail to the drawings and having reference firstto the form of the invention shown in FIGS. 1 to 3 thereof, the roadtreadle of the present invention comprises an envelope or shell Edefined by a ytop wall 10, a bottom wall 12, opposite side walls 14 and16 and opposite end walls 18 and 20 and the switch members S, S encasedthereby, two of which are shown in the drawings. Each of the switchmembers S comprises normally open contact elements movable to switchclosing condition by the treadle depression of the top wall 10 of theenvelope E, the said contact elements for each switch member comprisinga metal base plate 22 as the lower contact element (serving for bothswitch members) and a spring steel plate 24 as the upper contactelement, the upper contact elements 24, 24 being supportingly spacedfrom the lower contact element 22 by an encircling mount 26.

The shell or envelope E is m-ade or fashioned from an elastomericmaterial possessing inherent resilience, flexibility and abrasiveresistance. Such an elastomeric mate rial is either a synthetic rubbersuch las neoprene or G.R.S. rubber as illustrated in the drawings or maybe a polyurethane as hereinafter described. Such an elastomeric materialprovides flexibility required for transmitting pressure applied to thetop wall of the envelope E to operate the encased switches S, S. In thekform of the invention shown in FIGS. l to 3 the structure of the switchelements and particularly the provision of cavities 28, 28 between thecontact elements of the switches define means for enhancing to a desireddegree the ilexibility of the top wall of the envelope in the areas thatare subject to treadle depression.

In carrying out the principles of the present'invention in all of theconstructional forms shown in the drawings,

the envelope E comprising the elastomeric material in.

itself possessing resilience, flexibility, and abrasive resistance, iscombined with wear improving means incorporated into surface areas ofthe top wall of the elastomeric envelope between and spaced by adjoiningflexibility areas thereof, said means comprising wear pads havingabrasive resistance greater than the inherent abrasive resistance ofsaid adjoining iiexibility areas.

Reverting now to the form of the invention shown in FIGS. 1 to 3, thewear improving pads arey located in and confined to the normal pathareas of the wheels of a passing vehicle. To this end the top wall 10 ofthe envelope is subdivided at its surface into the spaced ilexibilityareas designated F, F and wear pad areas into which are incorporatedwear pads W, W, the wear pads bei-ng arranged in the normal path of thewheels of a vehicle and between and spaced by the adjoining flexibilityareas F, F.

Where the elastomeric material of the envelope E comprises a syntheticrubber, the wear pads W, W are made of a polyurethane material.Polyurethanes comprise a group of synthetics with end productscharacterized as flexible and elastomeric rubber-like products ofsuperior strength, good elasticity, extremely good abrasion resistanceand hardness, and resistance to greases, oils, and solvents. Basicallythey are reaction products of polyols and isocyanates, the majorcontributing variable being the polymers or polyfunctional resins whichcan be alkyd, polyesters or polyethers. These resins are of a classbased `on polyhydric alcohols and organic or polybasic acids. Adipicacid and glycols of various types are the prime source of polyols usedin the manufacture of polyurethanes. The polyurethane elastomer selectedfor the wear pads W, W is preferably a liquid polyurethane produced bythe E. I. du Pont Company and sold as their Adiprene L liquid urethaneelastomer', the preferred Adiprene product for use in the making of thetreadle wear pad of the present invention being Du Ponts Adiprene L-lOOwhich yields a solidified product having a durometer hardness of 88-90and Adiprene L-420 which yields a solidilied product having a durometerhardness of 80.

While such polyurethane pads also have an inherent flexibility andresilience, they possess an abrasive resistance substantially greaterthan the inherent abrasive resistance of the rubber elastomer of theflexibility areas F, F of the envelope E.

For mounting the wear pads W, W into the spaces provided therefor in thetop wall of the envelope E, the surface of the neoprene or G.R.S. rubberwhich is first produced in molded cured form, is first cleaned of oilsand grease by the use of a solvent such as methyl ethyl ketone. Thecleaned surface then receives a coat of a suitable cement. This isallowed to air dry. The liquid polyurethane is then poured onto theprepared surface and is then subjected to a heat treatment of 212 F. fora period of three hours.

As indicated heretofore, the body of the envelope E may also be made ofa polyurethane material, in which event the wear pads W, W are madeeither of a higher wear resistant polyethylene or of a wear resistancerigid material such as steel. In this case the envelope E is firstproduced as follows: The metal base plate 22 is suitably prepared andplaced in a forming receptacle (not shown) whose dimensions conform tothe desired final size of the treadle being manufactured. The treadle ofFIGS. 1 to 3 is generally made having a length of from 8 feet to 10 feetand a width of 4 inches to 14 inches (nominally 10% inches) and a heightof l inch. The upper spring contact plates 24, 24 are mounted spacedlyfrom the lower metal contact plate 22 by means of the mounts 26 whichencircle the cavities 28, 28, the upper contact spring plates beingframed in the mounts 26, which latter are made of rubber or a likematerial designed to seal the enclosure cavities 28, 28. With theseparts of the switch members S, S assembled and with suitable fixtures orplugs being also set up in the receptacle for forming the road mountingorifices 39, 30, the liquid polyurethane is then poured into the formingreceptacle, the liquid polyurethane flowing about and encasing theswitch members S, S. In the assembling step of the switch members theproper conducting lead wires 32, 32 (see FIG. l) are connected to the`contact elements 24, 24 of the switch members. The next operation isthe curing of the thus completed assembly in a dry heat at a temperatureof about 180 F. for the period of about one hour. Where the wear pads W,W now comprise a polyurethane material having a higher abrasionresistance than the polyurethane material of the envelope E, the wearpads are incorporated into the top wall of the envelope as follows: Thesurface of the cured polyurethane is washed with xylene, and the uncuredpolyurethane used to form the wear pads is then poured onto the preparedsurface. The assembly is then subjected to a dry heat of 212 F. for aperiod of an hour. Where the wear pads W, W are made to comprise a rigidhigh abrasive material such as steel, the surface of the steel is irstprepared by shot blasting or chemical etching; and in either case thesteel is treated such as in a vapor degreaser to remove oils and grease.The surface of the steel is then coated with a cement; and a tack coatof a suitable cement is then applied to the surface of the seat for thepads W, W and allowed to dry. The wear pads are then applied; and undera high pressure and temperature the assembly is cured.

In each of the described structures in the form of the invention shownin FIGS. 1 to 3, there are thus wear improving pads W, W incorporatedinto surface areas of the top wall of the elastomeric envelope E betweenand spaced by adjoining flexibility areas F, F thereof, said wearimproving pads having abrasive resistance greater than the inherentresistance of said adjoining flexibility areas, with the result that theWear resistance of the switch treadle and hence the life expectancythereof is improved while the necessary and predetermined ilexibility isprovided and retained. In the form of the invention depicted in FIGS. 1to 3 the life expectancy of the treadle switch is extended also byconfining the wear improving pads to the areas defined by the normalpath of the wheels of a passing vehicle.

In FIGS. 4 to 6 of the drawings is shown a second form of the inventionwherein features of treadle flexibility and resilience are obtained inanother way customarily employed with rubber treadles. In this form ofthe invention the treadle envelope E comprises a shell having a top wall10', a bottom wall 12', side walls 14 and 16' and end walls 18 and 20'encasing switch members S, S', the contact elements of which (notindependently shown) are indicated by the mark X. As before the envelopeE' is made of a rubber elastomeric material possessing an inherentresilience, abrasive resistance and flexibility. In this form a roadtreadle the flexibility of the road treadle is enhanced by the provisionof flex grooves in the top wall of the road treadle as Well as openspaces in the body of the vtreadle as will be presently described. Thisform of road treadle is made by assembling with an uncured body ofrubber a steel supporting plate 33 functioning to rigidify the structureand a number of bars (four in number) enveloped by a rubber impregnatedcloth, these bars serving to produce the cavities 34, 34 and a number ofbars (three in number) serving to form the additional spaces 36, 36.This assembly is placed into a mold shaped to the form shown incross-section in FIG. 5, the form being such as to provide or produceflexing grooves 38, 38l in the top wall of the envelope and seats 39, 39for the subsequent incorporation therein of wear pads W', W. After themolding of this assembly, the bars which form the cavities 34 arewithdrawn leaving in the cavities the rubber impregnated cloth 40 whichnow defines the walls of the cavities 34, 34, the withdrawing of theremaining bars leaving or producing the cavities 36, 36, which latterfunction, as a supplement to the flexing grooves 38, 38 for enhancingthe flexibility of the treadle structure to the required degree.

In this form of construction there is also produced at the barwithdrawing end of the treadle shell, integral socalled boots 42., 42 ofthe rubber elastomer through which previously attached lead wires 44extend, the bars being withdrawn through these extending boots, afterwhich sealing means are inserted to seal the lead wires at this end ofthe treadle. l

In this form of the treadle structure wear pads W', W' are incorporate-dinto the top wall of the treadle envelope E' by being mounted in theseats 39 provided therefor,

the wear pads W', W being thus incorporated into the surface areas ofthe top wall of the envelope between and spaced by the adjoiningflexibility areas vprovided by the flexing grooves 38, 38, theflexibility in this case being further supplemented by the similarlyspaced provision of the cavities 36, 36. y

In this form ofthe structure the flexing grooves 38, 38 comprise aplurality of grooves arranged longitudinally of the envelope E andspaced transversely of the top wall of the envelope, the wear pads W', Walso extending longitudinally of the envelope E and being locatedbetween and in alternatingy relation with the longitudinal flexinggrooves 38, 38.

Where, as indicated, the material of the envelope E is an elastomer suchas neoprene or G.R.S. rubber, the material of the pads W', W is apolyurethane of the class heretofore mentioned, namely a curedpolyurethane obtained from a liquid polyurethane such as the AdipreneL-l or the Adiprene L-420 liquid urethane elastomer (produced and soldby the E. I. du Pont Company), the former yielding a solidified producthaving a durometer hardness of 88-90 and the latter yielding asolidified produ-ct having a durometer hardness of 80. Such wear padsare incorporated into the top w-all of the envelope E in the s-ame wayas heretofore described in connection with the making of the envelope E,where the parts of the latter are formed `with the similar materials.

The road treadle of FIGS. 4 to 6 may also be produced by making theenvelope E of a polyurethane material such as the one having a lowerdurometer hardness and by then making the pads W', W thereof either of apolyurethane m-aterial having a greater durometer hardness or by makingthe same of a metal such as a steel plate or bar. In this event theenvelope E is made by pouring the liquid polyurethane into a formingreceptacle in which are assembled the steel supporting plate 33, thefour bars enveloped by the rubber impregnated cloth serving to producethe cavities 34, 34 and the three bars serving to form the additionalspaces 36, 36, this assembly being arranged in the forming receptaclereversely to that shown in FIG. 5 of the drawings, suitable membersbeing set in the bottom of the receptacle for forming-the flex grooves38, 38

yand the seats 39, 39V in the top wall of the treadle.

With these parts thus assembled the liquid polyurethane is poured intothe forming receptacle producing, after the heating step (curing is at adry'heat at a ternperature of about 180 F. for the period of about onehour), the cast treadle portrayed in the drawings. After theseoperations the -bars forming the cavities 34, 34 and the spaces 36, 36are withdrawn in the manner previously described and switch members S',S are then inserted into the cavities 34, 34 and the treadle thereuponsealed. The pads W', W are then mounted and Secured to the seats 39, 39provided therefor. These wear pads made either of a polyureth-ane havinga greater abrasion resistance lthan the polyurethane of the envelope Eor made of a metal such as a steel bar or plate are secured in theirseats in the same Ways as heretofore described for these respectivematerials.

Again here as in the first form of the invention the wear improving padsare incorporated into surface areas of the top wall of the elastomericenvelope between and spaced by adjoining flexibility areas thereof, andthe wear improvingpads introduce an abrasive resistance greater than theinherent abrasive resistance of the flexibility areas of the treadlewhich adjoin the location of the Wear pads.

The road treadle depicted in FIGS. 7 to 9 of the drawings embodies thesame structure as the road treadle depicted in FIGS. 4 to 6 of thedrawings with the exception that in the treadle of FIGS. 7 to 9, inaddition yto the plurality of longitudinal flexing grooves, Ithere areprovided a series of flexing grooves arranged betweenk said longitudinalflexingA grooves and spaced longitudinally of the top wall of theenvelope, with wear pads located and -arranged in the spaces providedbetween said plurality and said series `of flexing grooves. In this formof treadle structure the parts similar to Ithe parts which are the sameas the treadle structure of FIGS. 4 to 6 are designated by the samereference characters. The additional series of flexing grooves which arearranged -between the longitudinal grooves 38, 38 and which are spa-cedlongitudinally of the top wall of the envelope are designated by thereference characters 382, 382. The wear pads which are then loc-ated andarranged in all of the spaces provided by the plurality of flexinggrooves 38, 38 and the series of flexing grooves 382, 382 are designatedby the reference .character W2. With this construction flexibility ofthe treadle structure as a whole is produced both longitudinally andtransversely of the treadle structure to a maximum degree.

In all of the forms of the road treadle switch disclosed, a high wearresistant material in the form of the wear resistant pads or strips isplaced in the areas that have been subjected to extreme wear. Therequired flexibility for the satisfactory operation of the treadleswitches is provided by the juncture of flexible elastomer inbetween thepads or strips of the wear resistant material. In all of these forms ofthe invention the elastomer is depressed in the areas or grooves thatreceive practically :little or no abrasive wear. As a result a longerlife road treadle switch is provi-ded with increased efficient operationthereof at toll installations of turnpikes, bridges, etc.

The structures, operation and uses as well Ias theadvantages secured byroad treadle switches of the present invention will thus be apparentfrom the above detailed description thereof. It will be further apparentthat many changes may be made therein without departing yfrom the spiritof the invention defined in the following claims.

I cl-aim:

1. A road treadle switch comprising an envelope defined by a top wall, abottom wall, opposite side walls, and opposite end walls, and switchmembers encased by said envelope, the said switch members comprisingnormally open contact elements movable to switch closing condition bytreadle depression of a passing vehicle acting on the top Wall of saidenvelope, characterized by the said envelope comprising an elastomericmaterial possessing inherent resilience, flexibility and abrasiveresistance, said elastomeric material providing in the top wallr ofVsaid envelope spaced areas lpossessing said inherent resilience,flexibility and abrasive resistance, combined with wear improving meansincorporated into surface areas of the top wall of said elastomericenvelope between land spaced by said flexibility areas thereof, saidmeans comprising wear pads having abrasive resistance greater than theinherent abrasive resistance of said 'adjoining flexibility areas.

2. The road treadle switch of claim 1 in which the wear improving padsare located in andconfined -to the normal path area of the vehicle.

3. The' road treadle switch of claim 1 in which the elastomeric envelopeembodies means for enhancing the inherent flexibility of the top wallthereof in the areas that are subject to treadle depression, and thesaid Wear pads are located in spaced relation to said last mentionedareas.

4. The road treadle switch of claim 3 in which the means for enhancingthe inherent flexibility of the top wall of the envelope comprise aplurality of longitudinal flexing grooves arranged in said flexibilityareas of the top wall of the envelope and spaced transversely of the topwall of the envelope, and the rear pads are located and arranged betweensaid flexing grooves.

5. The road treadle switch of claim 1 in which the elastomeric materialof the envelope is selected from the group consisting of rubber andpolyurethane, and the material of the wearV pads is selected from thegroup consisting of a polyurethane or a metal, the polyurethane of v thewear pads having a higher abrasion resistance than elastomeric materialof the envelope is selected from the group consisting of rubber andpolyurethane, and the material of the wear pads is selected from thegroup consisting of a polyurethane or a metal, the polyurethane of thewear pads having a higher abrasion resistance than the rubber andpolyurethane of the envelope.

7. The road tre-adle switch of claim 3 in which the material of theenvelope is rubber .and the material of the wear pad is selected fromthe group consisting of a polyurethane and steel.

8. The road treadle switch of claim 3 in which the means for enhancingthe inherent flexibility of the top wall of the envelope comprise aplurality of longitudin-al flexing grooves spaced transversely of thetop wall of the envelope land a series of leXing grooves arrangedbetween Asaid longitudinal grooves and spaced longitudinally of the topwall of the envelope, and the wear pads are located and arnanged in thespaces between said plurality and series of ilexing grooves.

No references cited.

BERNARD A. GILH-EANY, Primary Examiner.

H. LEWITTER Assistant Examiner.

1. A ROAD TREADLE SWITCH COMPRISING AN ENVELOPE DEFINED BY A STOP WALL,A BOTTOM WALL, OPPOSITE SIDE WALLS, AND OPPOSITE END WALLS, AND SWITCHMEMBERS ENCASED BY SAID ENVELOPE, THE SAID SWITCH MEMBERS COMPRISINGNORNALLY OPEN CONTACT ELEMENTS MOVABLE TO SWITCH CLOSING CONDITION BYTREADLE DEPRESSION OF A PASSSING VEHICLE ACTING ON THE TOP WALL OF SAIDENVELOPE, CHARACTERIZED BY THE SAID ENVELOPAE COMPRISING AN ELASTOMERICMATERIAL POSSESSING INHERENT RESILIENT, FLEXIBILITY AND ABRASIVERESISTANCE, SAID ELASTOMERIC MATERIAL PROVIDING IN THE TOP WALL OF SAIDENVELOPE SPACED AREAS POSSESSING SAID INHERENT RESILIENCE, FLEXIBILITYAND ABRASIVE RESISTANCE, COMBINED WITH WEAR IMPROVING MEANS INCORPORATEDINTO SURFACE AREAS OF THE TOP WALL OF SAID ELASTOMERIC ENVELOPE BETWEENAND SPACED BY SAID FLEXIBILITY AREAS THEREOF, SAID MEANS COMPRISING WEARPADS HAVING ABRASIVE RESISTANCE GREATER THAN THE INHERENT ABRASIVERESISTANCE OF SAID ADJOINING FLEXIBILITY AREAS.